366 HYALONEMA (PHIALONEMA) PATERIFERUM. 



base 4-6 jii, maximum 8-27 ai; and in form F base 3.5-6 m, maximmn 7-16 yu. 

 The maximum thickness of the distal ray, together with the spines, is in the 

 ordinary pinules with laterals of moderate length usually 8-16 m; distal rays 

 with a maximum thickness of only 6 m or less are found only among those forms 

 with long laterals, which pass into the microhexactines. The lateral rays are 

 in the forms A and B, according to Wilson {loc. cit.), pointed and nearly or quite 

 smooth. In the forms C, D, E, and F they are also usually pointed, but smooth 

 only exceptionally; as a rule they are provided with sparse, but rather large and 

 conspicuous spines. Sometimes I observed lateral rays with much larger and 

 more numerous spines which, in respect to spinulation, resembled the distal ray. 

 The lateral rays are in the forms A and B, according to Wilson {loc. cit.), 

 30-40 u. long, in form C 13-44 fx, in form D 16-100 n, in form E 24-54 ^, and in 

 form F 26-63 /i. Tlie pinules with lateral rays more than 50 fi long are mostly 

 transitions to the microhexactines. In the ordinary pinules a sixth proximal 

 ray is present only quite exceptionally, and here hardly ever more than 30 /j. 

 long; in the pinules transitional to the microhexactines a proximal ray is gen- 

 erally met, and in these it attains a length of 50-100 m- In regard to the 

 spinulation, the proximal rays usually resembles the laterals. In some of the 

 forms transitional to the microhexactines, the proximal ray is spined in a similar 

 way to the distal. 



The pentactine pinules with elongated distal ray (Plate 52, fig. 15). The 

 distal ray of these spicules is in the forms A and B examined by Wilson {loc. 

 cit.) 300-400 IX long, in form D 240-315 m- In forms C and F I observed only 

 very few pinules of this kind. In these the distal ray was 350 ^ long. In 

 form E I failed to find any pinules of this kind. I ascribe the absence of these 

 spicules in this form and their scarcity in the preparations of forms C and F 

 to the fragmentary condition of the specimen of these forms. In the forms 

 C, D, and F the distal ray is 4.5-6.5 m thick at the base, conic, and generally 

 somewhat curved. It terminates in an exceedingly long and slender, spineless 

 terminal cone. Its middle-part bears small spines inclined towards the tip. 

 Its maximum transverse diameter, together with the spines, is 5-14 ix. In 

 forms A and B, examined by Wilson {loc. cit.), the distal ray is similar. The 

 lateral rays are pointed or, more rarely, rounded at the end. In the forms 

 A and B, examined by Wilson {loc. cit.), they are 40 jx long, in the forms C, D, 

 and F, 15-38 fi. 



The diactine pinules (Plate 52, fig. 16) appear as anisoactine, centrotyle 

 amphioxes with numerous spines on their distal ray, and occasionally also a few 



